参考的正点原子的代码

 

测试平台

stm32f429i-disco

配了一个gpio

时钟

gpio

 

/* USER CODE BEGIN 0 */typedef uint8_t u8;typedef uint32_t u32;u8 fac_us;void delay_init(u8 SYSCLK){    #if SYSTEM_SUPPORT_OS //?????? OS.        u32 reload;    #endif        HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);    //SysTick ??? HCLK    fac_us=SYSCLK; //?????? OS,fac_us ?????        #if SYSTEM_SUPPORT_OS //?????? OS.        reload=SYSCLK; //???????? ??? K        reload*=1000000/delay_ostickspersec; //?? delay_ostickspersec ??????        //reload ? 24 ????,???:16777216,? 180M ?,?? 0.745s ??        fac_ms=1000/delay_ostickspersec; //?? OS ?????????        SysTick->CTRL|=SysTick_CTRL_TICKINT_Msk;//?? SYSTICK ??        SysTick->LOAD=reload; //? 1/OS_TICKS_PER_SEC ?????        SysTick->CTRL|=SysTick_CTRL_ENABLE_Msk; //?? SYSTICK        #else    #endif}void delay_us(u32 nus){    u32 ticks;    u32 told,tnow,tcnt=0;    u32 reload=SysTick->LOAD; //LOAD ??    ticks=nus*fac_us; //??????    told=SysTick->VAL; //?????????    while(1)    {        tnow=SysTick->VAL;        if(tnow!=told)        {            if(tnow
     
      =ticks)break; //????/????????,???.        }    };}/* USER CODE END 0 */
     

int main(void){  /* USER CODE BEGIN 1 */  /* USER CODE END 1 */  /* MCU Configuration----------------------------------------------------------*/  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */  HAL_Init();  /* Configure the system clock */  SystemClock_Config();  /* Initialize all configured peripherals */  MX_GPIO_Init();  /* USER CODE BEGIN 2 */    delay_init(168);  /* USER CODE END 2 */  /* Infinite loop */  /* USER CODE BEGIN WHILE */  while (1)  {  /* USER CODE END WHILE */    HAL_GPIO_WritePin(GPIOF, GPIO_PIN_7, GPIO_PIN_SET);    delay_us(50);    HAL_GPIO_WritePin(GPIOF, GPIO_PIN_7, GPIO_PIN_RESET);    delay_us(50);  /* USER CODE BEGIN 3 */  }  /* USER CODE END 3 */}

 

 

 

实际测试, 函数调用能带来几百ns的误差.